Merge pull request #15952 from jerrywgz/fpn_ops

add distribute fpn proposals op, test=develop

paddle/fluid/API.spec

@@ -329,6 +329,7 @@ paddle.fluid.layers.polygon_box_transform (ArgSpec(args=['input', 'name'], varar
 paddle.fluid.layers.yolov3_loss (ArgSpec(args=['x', 'gtbox', 'gtlabel', 'anchors', 'anchor_mask', 'class_num', 'ignore_thresh', 'downsample_ratio', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '991e934c3e09abf0edec7c9c978b4691'))
 paddle.fluid.layers.box_clip (ArgSpec(args=['input', 'im_info', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '397e9e02b451d99c56e20f268fa03f2e'))
 paddle.fluid.layers.multiclass_nms (ArgSpec(args=['bboxes', 'scores', 'score_threshold', 'nms_top_k', 'keep_top_k', 'nms_threshold', 'normalized', 'nms_eta', 'background_label', 'name'], varargs=None, keywords=None, defaults=(0.3, True, 1.0, 0, None)), ('document', 'ca7d1107b6c5d2d6d8221039a220fde0'))
+paddle.fluid.layers.distribute_fpn_proposals (ArgSpec(args=['fpn_rois', 'min_level', 'max_level', 'refer_level', 'refer_scale', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '7bb011ec26bace2bc23235aa4a17647d'))
 paddle.fluid.layers.box_decoder_and_assign (ArgSpec(args=['prior_box', 'prior_box_var', 'target_box', 'box_score', 'box_clip', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', '005a5ae47d6c8fff721931d69d072b9f'))
 paddle.fluid.layers.accuracy (ArgSpec(args=['input', 'label', 'k', 'correct', 'total'], varargs=None, keywords=None, defaults=(1, None, None)), ('document', '9808534c12c5e739a10f73ebb0b4eafd'))
 paddle.fluid.layers.auc (ArgSpec(args=['input', 'label', 'curve', 'num_thresholds', 'topk', 'slide_steps'], varargs=None, keywords=None, defaults=('ROC', 4095, 1, 1)), ('document', 'e0e95334fce92d16c2d9db6e7caffc47'))

paddle/fluid/operators/detection/CMakeLists.txt

@@ -37,8 +37,10 @@ detection_library(box_decoder_and_assign_op SRCS box_decoder_and_assign_op.cc bo
 
 if(WITH_GPU)
   detection_library(generate_proposals_op SRCS generate_proposals_op.cc generate_proposals_op.cu DEPS memory cub)
+  detection_library(distribute_fpn_proposals_op SRCS distribute_fpn_proposals_op.cc distribute_fpn_proposals_op.cu DEPS memory cub)
 else()
   detection_library(generate_proposals_op SRCS generate_proposals_op.cc)
+  detection_library(distribute_fpn_proposals_op SRCS distribute_fpn_proposals_op.cc)
 endif()
 
 detection_library(roi_perspective_transform_op SRCS roi_perspective_transform_op.cc roi_perspective_transform_op.cu)

paddle/fluid/operators/detection/distribute_fpn_proposals_op.cc

+/* Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
+#include "paddle/fluid/operators/detection/distribute_fpn_proposals_op.h"
+
+namespace paddle {
+namespace operators {
+
+class DistributeFpnProposalsOp : public framework::OperatorWithKernel {
+ public:
+  using framework::OperatorWithKernel::OperatorWithKernel;
+
+  void InferShape(framework::InferShapeContext* ctx) const override {
+    PADDLE_ENFORCE(ctx->HasInput("FpnRois"),
+                   "Input(FpnRois) shouldn't be null");
+    PADDLE_ENFORCE_GE(
+        ctx->Outputs("MultiFpnRois").size(), 1UL,
+        "Outputs(MultiFpnRois) of DistributeOp should not be empty");
+    size_t min_level = static_cast<size_t>(ctx->Attrs().Get<int>("min_level"));
+    size_t max_level = static_cast<size_t>(ctx->Attrs().Get<int>("max_level"));
+    PADDLE_ENFORCE_GE(max_level, min_level,
+                      "max_level must not lower than min_level");
+    // Set the output shape
+    size_t num_out_rois = max_level - min_level + 1;
+    std::vector<framework::DDim> outs_dims;
+    outs_dims.reserve(num_out_rois);
+    for (size_t i = 0; i < num_out_rois; ++i) {
+      framework::DDim out_dim = {-1, 4};
+      outs_dims.push_back(out_dim);
+    }
+    ctx->SetOutputsDim("MultiFpnRois", outs_dims);
+    ctx->SetOutputDim("RestoreIndex", {1, -1});
+  }
+
+ protected:
+  framework::OpKernelType GetExpectedKernelType(
+      const framework::ExecutionContext& ctx) const override {
+    auto data_type = framework::GetDataTypeOfVar(ctx.InputVar("FpnRois"));
+    return framework::OpKernelType(data_type, platform::CPUPlace());
+  }
+};
+
+class DistributeFpnProposalsOpMaker : public framework::OpProtoAndCheckerMaker {
+ public:
+  void Make() override {
+    AddInput("FpnRois", "(LoDTensor) The rois at all levels in shape (-1, 4)");
+    AddOutput("MultiFpnRois", "(LoDTensor) Output with distribute operator")
+        .AsDuplicable();
+    AddOutput("RestoreIndex",
+              "(Tensor) An array of positive number which is "
+              "used to restore the order of FpnRois");
+    AddAttr<int>("min_level",
+                 "The lowest level of FPN layer where the"
+                 " proposals come from");
+    AddAttr<int>("max_level",
+                 "The highest level of FPN layer where the"
+                 " proposals come from");
+    AddAttr<int>("refer_level",
+                 "The referring level of FPN layer with"
+                 " specified scale");
+    AddAttr<int>("refer_scale",
+                 "The referring scale of FPN layer with"
+                 " specified level");
+    AddComment(R"DOC(
+This operator distribute all proposals into different fpn level,
+ with respect to scale of the proposals, the referring scale and
+ the referring level. Besides, to restore the order of proposals,
+we return an array which indicate the original index of rois in
+ current proposals.
+)DOC");
+  }
+};
+}  // namespace operators
+}  // namespace paddle
+
+namespace ops = paddle::operators;
+REGISTER_OPERATOR(distribute_fpn_proposals, ops::DistributeFpnProposalsOp,
+                  ops::DistributeFpnProposalsOpMaker,
+                  paddle::framework::EmptyGradOpMaker);
+REGISTER_OP_CPU_KERNEL(distribute_fpn_proposals,
+                       ops::DistributeFpnProposalsOpKernel<float>,
+                       ops::DistributeFpnProposalsOpKernel<double>);

paddle/fluid/operators/detection/distribute_fpn_proposals_op.cu

+/* Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
+#include <paddle/fluid/memory/allocation/allocator.h>
+#include "cub/cub.cuh"
+#include "paddle/fluid/memory/memcpy.h"
+#include "paddle/fluid/operators/detection/distribute_fpn_proposals_op.h"
+#include "paddle/fluid/operators/gather.cu.h"
+#include "paddle/fluid/platform/cuda_primitives.h"
+#include "paddle/fluid/platform/for_range.h"
+
+namespace paddle {
+namespace operators {
+
+using Tensor = framework::Tensor;
+using LoDTensor = framework::LoDTensor;
+
+static constexpr int kNumCUDAThreads = 512;
+static constexpr int kNumMaxinumNumBlocks = 4096;
+
+#define CUDA_1D_KERNEL_LOOP(i, n)                              \
+  for (int i = blockIdx.x * blockDim.x + threadIdx.x; i < (n); \
+       i += blockDim.x * gridDim.x)
+
+int const BBoxSize = 4;
+
+struct RangeInitFunctor {
+  int start_;
+  int delta_;
+  int* out_;
+  __device__ void operator()(size_t i) { out_[i] = start_ + i * delta_; }
+};
+
+static inline int NumBlocks(const int N) {
+  return std::min((N + kNumCUDAThreads - 1) / kNumCUDAThreads,
+                  kNumMaxinumNumBlocks);
+}
+
+static inline void TransLoD(const int* length_lod, const int lod_size,
+                            int* offset_lod) {
+  int offset = 0;
+  for (int i = 0; i < lod_size; ++i) {
+    offset_lod[i] = offset;
+    offset += length_lod[i];
+  }
+}
+
+template <typename T>
+static __device__ inline T RoIArea(const T* box, bool normalized) {
+  if (box[2] < box[0] || box[3] < box[1]) {
+    // If coordinate values are is invalid
+    // (e.g. xmax < xmin or ymax < ymin), return 0.
+    return static_cast<T>(0.);
+  } else {
+    const T w = box[2] - box[0];
+    const T h = box[3] - box[1];
+    if (normalized) {
+      return w * h;
+    } else {
+      // If coordinate values are not within range [0, 1].
+      return (w + 1) * (h + 1);
+    }
+  }
+}
+
+template <class T>
+static __global__ void GPUDistFpnProposalsHelper(
+    const int nthreads, const T* rois, const int lod_size,
+    const int refer_level, const int refer_scale, const int max_level,
+    const int min_level, int* roi_batch_id_data, int* sub_lod_list,
+    int* target_lvls) {
+  CUDA_1D_KERNEL_LOOP(i, nthreads) {
+    const T* offset_roi = rois + i * BBoxSize;
+    int roi_batch_ind = roi_batch_id_data[i];
+    // get the target level of current rois
+    T roi_area = RoIArea(offset_roi, false);
+    T roi_scale = sqrt(roi_area);
+    int tgt_lvl = floor(log2(roi_scale / refer_scale) + refer_level);
+    tgt_lvl = min(max_level, max(tgt_lvl, min_level));
+    target_lvls[i] = tgt_lvl;
+    // compute number of rois in the same batch and same target level
+    platform::CudaAtomicAdd(sub_lod_list + tgt_lvl * lod_size + roi_batch_ind,
+                            1);
+  }
+}
+
+template <typename DeviceContext, typename T>
+class GPUDistributeFpnProposalsOpKernel : public framework::OpKernel<T> {
+ public:
+  void Compute(const framework::ExecutionContext& ctx) const override {
+    auto* fpn_rois = ctx.Input<paddle::framework::LoDTensor>("FpnRois");
+
+    auto multi_fpn_rois = ctx.MultiOutput<LoDTensor>("MultiFpnRois");
+    auto* restore_index = ctx.Output<Tensor>("RestoreIndex");
+
+    const int min_level = ctx.Attr<int>("min_level");
+    const int max_level = ctx.Attr<int>("max_level");
+    const int refer_level = ctx.Attr<int>("refer_level");
+    const int refer_scale = ctx.Attr<int>("refer_scale");
+    int num_level = max_level - min_level + 1;
+
+    // check that the fpn_rois is not empty
+    PADDLE_ENFORCE_EQ(fpn_rois->lod().size(), 1UL,
+                      "DistributeFpnProposalsOp need 1 level of LoD");
+
+    auto fpn_rois_lod = fpn_rois->lod().back();
+    int lod_size = fpn_rois_lod.size() - 1;
+    int roi_num = fpn_rois_lod[lod_size];
+
+    auto& dev_ctx = ctx.template device_context<DeviceContext>();
+
+    // get batch id by lod in CPU
+    Tensor roi_batch_id_list;
+    roi_batch_id_list.Resize({roi_num});
+    int* roi_batch_id_data =
+        roi_batch_id_list.mutable_data<int>(platform::CPUPlace());
+    for (int n = 0; n < lod_size; ++n) {
+      for (size_t i = fpn_rois_lod[n]; i < fpn_rois_lod[n + 1]; ++i) {
+        roi_batch_id_data[i] = n;
+      }
+    }
+    // copy batch id list to GPU
+    Tensor roi_batch_id_list_gpu;
+    framework::TensorCopySync(roi_batch_id_list, dev_ctx.GetPlace(),
+                              &roi_batch_id_list_gpu);
+
+    Tensor sub_lod_list;
+    sub_lod_list.Resize({num_level, lod_size});
+    int* sub_lod_list_data = sub_lod_list.mutable_data<int>(dev_ctx.GetPlace());
+    Tensor target_lvls;
+    target_lvls.Resize({roi_num});
+    int* target_lvls_data = target_lvls.mutable_data<int>(dev_ctx.GetPlace());
+
+    int blocks = NumBlocks(roi_num);
+    int threads = kNumCUDAThreads;
+
+    // get target levels and sub_lod list
+    GPUDistFpnProposalsHelper<T><<<blocks, threads>>>(
+        roi_num, fpn_rois->data<T>(), lod_size, refer_level, refer_scale,
+        max_level, min_level, roi_batch_id_list_gpu.data<int>(),
+        sub_lod_list_data, target_lvls_data);
+
+    Tensor index_in_t;
+    int* idx_in = index_in_t.mutable_data<int>({roi_num}, dev_ctx.GetPlace());
+    platform::ForRange<platform::CUDADeviceContext> for_range(dev_ctx, roi_num);
+    for_range(RangeInitFunctor{0, 1, idx_in});
+
+    Tensor keys_out_t;
+    int* keys_out = keys_out_t.mutable_data<int>({roi_num}, dev_ctx.GetPlace());
+    Tensor index_out_t;
+    int* idx_out = index_out_t.mutable_data<int>({roi_num}, dev_ctx.GetPlace());
+
+    // Determine temporary device storage requirements
+    size_t temp_storage_bytes = 0;
+    cub::DeviceRadixSort::SortPairsDescending<int, int>(
+        nullptr, temp_storage_bytes, target_lvls_data, keys_out, idx_in,
+        idx_out, roi_num);
+    // Allocate temporary storage
+    auto place = boost::get<platform::CUDAPlace>(dev_ctx.GetPlace());
+    auto d_temp_storage = memory::Alloc(place, temp_storage_bytes,
+                                        memory::Allocator::kScratchpad);
+
+    // Run sorting operation
+    // sort target level to get corresponding index
+    cub::DeviceRadixSort::SortPairsDescending<int, int>(
+        d_temp_storage->ptr(), temp_storage_bytes, target_lvls_data, keys_out,
+        idx_in, idx_out, roi_num);
+
+    int* restore_idx_data =
+        restore_index->mutable_data<int>({roi_num, 1}, dev_ctx.GetPlace());
+    // sort current index to get restore index
+    cub::DeviceRadixSort::SortPairsDescending<int, int>(
+        d_temp_storage->ptr(), temp_storage_bytes, idx_out, keys_out, idx_in,
+        restore_idx_data, roi_num);
+
+    Tensor offset_lod;
+    int* offset_lod_data =
+        offset_lod.mutable_data<int>({lod_size + 1}, dev_ctx.GetPlace());
+    for (int i = 0; i < num_level; ++i) {
+      Tensor sub_lod = sub_lod_list.Slice(i, i + 1);
+      int* sub_lod_data = sub_lod.data<int>();
+      // transfer length-based lod to offset-based lod
+      TransLoD(sub_lod_data, lod_size + 1, offset_lod_data);
+      int sub_rois_num = offset_lod_data[lod_size];
+      Tensor sub_idx = index_out_t.Slice(0, sub_rois_num);
+
+      multi_fpn_rois[i]->mutable_data<T>({sub_rois_num, kBoxDim},
+                                         dev_ctx.GetPlace());
+
+      GPUGather<T>(dev_ctx, *fpn_rois, sub_idx, multi_fpn_rois[i]);
+      framework::LoD lod;
+      std::vector<size_t> offset;
+      memory::Copy(platform::CPUPlace(), offset.data(), place, offset_lod_data,
+                   sizeof(int) * (lod_size + 1), 0);
+      lod.emplace_back(offset);
+      multi_fpn_rois[i]->set_lod(lod);
+    }
+  }
+};
+
+}  // namespace operators
+}  // namespace paddle
+
+namespace ops = paddle::operators;
+REGISTER_OP_CUDA_KERNEL(
+    distribute_fpn_proposals,
+    ops::GPUDistributeFpnProposalsOpKernel<paddle::platform::CUDADeviceContext,
+                                           float>,
+    ops::GPUDistributeFpnProposalsOpKernel<paddle::platform::CUDADeviceContext,
+                                           double>);

paddle/fluid/operators/detection/distribute_fpn_proposals_op.h

+/* Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License. */
+
+#pragma once
+
+#include <algorithm>
+#include <cmath>
+#include <cstring>
+#include <string>
+#include <vector>
+#include "paddle/fluid/framework/op_registry.h"
+#include "paddle/fluid/operators/detail/safe_ref.h"
+#include "paddle/fluid/operators/gather.h"
+#include "paddle/fluid/operators/math/math_function.h"
+
+namespace paddle {
+namespace operators {
+
+const int kBoxDim = 4;
+
+template <typename T>
+static inline T BBoxArea(const T* box, bool normalized) {
+  if (box[2] < box[0] || box[3] < box[1]) {
+    // If coordinate values are is invalid
+    // (e.g. xmax < xmin or ymax < ymin), return 0.
+    return static_cast<T>(0.);
+  } else {
+    const T w = box[2] - box[0];
+    const T h = box[3] - box[1];
+    if (normalized) {
+      return w * h;
+    } else {
+      // If coordinate values are not within range [0, 1].
+      return (w + 1) * (h + 1);
+    }
+  }
+}
+
+template <typename T>
+class DistributeFpnProposalsOpKernel : public framework::OpKernel<T> {
+ public:
+  void Compute(const framework::ExecutionContext& context) const override {
+    auto* fpn_rois = context.Input<paddle::framework::LoDTensor>("FpnRois");
+
+    auto multi_fpn_rois =
+        context.MultiOutput<paddle::framework::LoDTensor>("MultiFpnRois");
+
+    auto* restore_index =
+        context.Output<paddle::framework::Tensor>("RestoreIndex");
+
+    const int min_level = context.Attr<int>("min_level");
+    const int max_level = context.Attr<int>("max_level");
+    const int refer_level = context.Attr<int>("refer_level");
+    const int refer_scale = context.Attr<int>("refer_scale");
+    const int num_level = max_level - min_level + 1;
+
+    // check that the fpn_rois is not empty
+    PADDLE_ENFORCE_EQ(fpn_rois->lod().size(), 1UL,
+                      "DistributeFpnProposalsOp need 1 level of LoD");
+
+    auto fpn_rois_lod = fpn_rois->lod().back();
+    int fpn_rois_num = fpn_rois_lod[fpn_rois_lod.size() - 1];
+    std::vector<int> target_level;
+    // std::vector<int> target_level(fpn_rois_num, -1);
+    // record the number of rois in each level
+    std::vector<int> num_rois_level(num_level, 0);
+    std::vector<int> num_rois_level_integral(num_level + 1, 0);
+    for (int i = 0; i < fpn_rois_lod.size() - 1; ++i) {
+      Tensor fpn_rois_slice =
+          fpn_rois->Slice(fpn_rois_lod[i], fpn_rois_lod[i + 1]);
+      const T* rois_data = fpn_rois_slice.data<T>();
+      for (int j = 0; j < fpn_rois_slice.dims()[0]; ++j) {
+        // get the target level of current rois
+        T roi_scale = std::sqrt(BBoxArea(rois_data, false));
+        int tgt_lvl =
+            std::floor(std::log2(roi_scale / refer_scale) + refer_level);
+        tgt_lvl = std::min(max_level, std::max(tgt_lvl, min_level));
+        target_level.push_back(tgt_lvl);
+        num_rois_level[tgt_lvl - min_level]++;
+        rois_data += kBoxDim;
+      }
+    }
+    // define the output rois
+    // pointer which point to each level fpn rois
+    std::vector<T*> multi_fpn_rois_data(num_level);
+    // lod0 which will record the offset information of each level rois
+    std::vector<std::vector<size_t>> multi_fpn_rois_lod0;
+    for (int i = 0; i < num_level; ++i) {
+      // allocate memory for each level rois
+      multi_fpn_rois[i]->mutable_data<T>({num_rois_level[i], kBoxDim},
+                                         context.GetPlace());
+      multi_fpn_rois_data[i] = multi_fpn_rois[i]->data<T>();
+      std::vector<size_t> lod0(1, 0);
+      multi_fpn_rois_lod0.push_back(lod0);
+      // statistic start point for each level rois
+      num_rois_level_integral[i + 1] =
+          num_rois_level_integral[i] + num_rois_level[i];
+    }
+    restore_index->mutable_data<int>({1, fpn_rois_num}, context.GetPlace());
+    int* restore_index_data = restore_index->data<int>();
+    std::vector<int> restore_index_inter(fpn_rois_num, -1);
+    // distribute the rois into different fpn level by target level
+    for (int i = 0; i < fpn_rois_lod.size() - 1; ++i) {
+      Tensor fpn_rois_slice =
+          fpn_rois->Slice(fpn_rois_lod[i], fpn_rois_lod[i + 1]);
+      const T* rois_data = fpn_rois_slice.data<T>();
+      size_t cur_offset = fpn_rois_lod[i];
+      // std::vector<size_t > lod_offset[num_level];
+      for (int j = 0; j < num_level; j++) {
+        multi_fpn_rois_lod0[j].push_back(multi_fpn_rois_lod0[j][i]);
+      }
+      for (int j = 0; j < fpn_rois_slice.dims()[0]; ++j) {
+        int lvl = target_level[cur_offset + j];
+        memcpy(multi_fpn_rois_data[lvl - min_level], rois_data,
+               kBoxDim * sizeof(T));
+        multi_fpn_rois_data[lvl - min_level] += kBoxDim;
+        int index_in_shuffle = num_rois_level_integral[lvl - min_level] +
+                               multi_fpn_rois_lod0[lvl - min_level][i + 1];
+        restore_index_inter[index_in_shuffle] = cur_offset + j;
+        multi_fpn_rois_lod0[lvl - min_level][i + 1]++;
+        rois_data += kBoxDim;
+      }
+    }
+    for (int i = 0; i < fpn_rois_num; ++i) {
+      restore_index_data[restore_index_inter[i]] = i;
+    }
+    // merge lod information into LoDTensor
+    for (int i = 0; i < num_level; ++i) {
+      framework::LoD lod;
+      lod.emplace_back(multi_fpn_rois_lod0[i]);
+      multi_fpn_rois[i]->set_lod(lod);
+    }
+  }
+};
+}  // namespace operators
+}  // namespace paddle

python/paddle/fluid/layers/detection.py

@@ -51,6 +51,7 @@ __all__ = [
     'yolov3_loss',
     'box_clip',
     'multiclass_nms',
+    'distribute_fpn_proposals',
     'box_decoder_and_assign',
 ]
 
@@ -2224,6 +2225,79 @@ def multiclass_nms(bboxes,
     return output
 
 
+def distribute_fpn_proposals(fpn_rois,
+                             min_level,
+                             max_level,
+                             refer_level,
+                             refer_scale,
+                             name=None):
+    """
+    In Feature Pyramid Networks (FPN) models, it is needed to distribute all 
+    proposals into different FPN level, with respect to scale of the proposals,
+    the referring scale and the referring level. Besides, to restore the order
+    of proposals, we return an array which indicates the original index of rois
+    in current proposals. To compute FPN level for each roi, the formula is 
+    given as follows:
+    
+    .. math::
+
+        roi\_scale &= \sqrt{BBoxArea(fpn\_roi)}
+
+        level = floor(&\log(\\frac{roi\_scale}{refer\_scale}) + refer\_level)
+
+    where BBoxArea is a function to compute the area of each roi.
+
+    Args:
+        fpn_rois(variable): The input fpn_rois, the second dimension is 4.
+        min_level(int): The lowest level of FPN layer where the proposals come 
+                        from.
+        max_level(int): The highest level of FPN layer where the proposals
+                        come from.
+        refer_level(int): The referring level of FPN layer with specified scale.
+        refer_scale(int): The referring scale of FPN layer with specified level.
+        name(str|None): The name of this operator.        
+
+    Returns:
+        tuple: 
+               A tuple(multi_rois, restore_ind) is returned. The multi_rois is 
+               a list of segmented tensor variables. The restore_ind is a 2D 
+               Tensor with shape [N, 1], N is the number of total rois. It is
+               used to restore the order of fpn_rois.
+
+    Examples:
+        .. code-block:: python
+
+            fpn_rois = fluid.layers.data(
+                name='data', shape=[4], dtype='float32', lod_level=1)
+            multi_rois, restore_ind = fluid.layers.distribute_fpn_proposals(
+                fpn_rois=fpn_rois,
+                min_level=2,
+                max_level=5,
+                refer_level=4,
+                refer_scale=224)
+    """
+
+    helper = LayerHelper('distribute_fpn_proposals', **locals())
+    dtype = helper.input_dtype()
+    num_lvl = max_level - min_level + 1
+    multi_rois = [
+        helper.create_variable_for_type_inference(dtype) for i in range(num_lvl)
+    ]
+    restore_ind = helper.create_variable_for_type_inference(dtype='int32')
+    helper.append_op(
+        type='distribute_fpn_proposals',
+        inputs={'FpnRois': fpn_rois},
+        outputs={'MultiFpnRois': multi_rois,
+                 'RestoreIndex': restore_ind},
+        attrs={
+            'min_level': min_level,
+            'max_level': max_level,
+            'refer_level': refer_level,
+            'refer_scale': refer_scale
+        })
+    return multi_rois, restore_ind
+
+
 @templatedoc()
 def box_decoder_and_assign(prior_box,
                            prior_box_var,

python/paddle/fluid/tests/test_detection.py

@@ -504,5 +504,21 @@ class TestMulticlassNMS(unittest.TestCase):
             self.assertIsNotNone(output)
 
 
+class TestDistributeFpnProposals(unittest.TestCase):
+    def test_distribute_fpn_proposals(self):
+        program = Program()
+        with program_guard(program):
+            fpn_rois = fluid.layers.data(
+                name='data', shape=[4], dtype='float32', lod_level=1)
+            multi_rois, restore_ind = layers.distribute_fpn_proposals(
+                fpn_rois=fpn_rois,
+                min_level=2,
+                max_level=5,
+                refer_level=4,
+                refer_scale=224)
+            self.assertIsNotNone(multi_rois)
+            self.assertIsNotNone(restore_ind)
+
+
 if __name__ == '__main__':
     unittest.main()

python/paddle/fluid/tests/unittests/test_distribute_fpn_proposals_op.py

+#    Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+import unittest
+import numpy as np
+import math
+import sys
+from op_test import OpTest
+
+
+class TestDistributeFPNProposalsOp(OpTest):
+    def set_data(self):
+        self.init_test_case()
+        self.make_rois()
+        self.rois_fpn, self.rois_idx_restore = self.calc_rois_distribute()
+        self.inputs = {'FpnRois': (self.rois[:, 1:5], self.rois_lod)}
+        self.attrs = {
+            'max_level': self.roi_max_level,
+            'min_level': self.roi_min_level,
+            'refer_scale': self.canonical_scale,
+            'refer_level': self.canonical_level
+        }
+        output = [('out%d' % i, self.rois_fpn[i])
+                  for i in range(len(self.rois_fpn))]
+        self.outputs = {
+            'MultiFpnRois': output,
+            'RestoreIndex': self.rois_idx_restore
+        }
+
+    def init_test_case(self):
+        self.roi_max_level = 5
+        self.roi_min_level = 2
+        self.canonical_scale = 224
+        self.canonical_level = 4
+        self.images_shape = [512, 512]
+
+    def boxes_area(self, boxes):
+        w = (boxes[:, 2] - boxes[:, 0] + 1)
+        h = (boxes[:, 3] - boxes[:, 1] + 1)
+        areas = w * h
+        assert np.all(areas >= 0), 'Negative areas founds'
+        return areas
+
+    def map_rois_to_fpn_levels(self, rois, lvl_min, lvl_max):
+        s = np.sqrt(self.boxes_area(rois))
+        s0 = self.canonical_scale
+        lvl0 = self.canonical_level
+        target_lvls = np.floor(lvl0 + np.log2(s / s0 + 1e-6))
+        target_lvls = np.clip(target_lvls, lvl_min, lvl_max)
+        return target_lvls
+
+    def get_sub_lod(self, sub_lvl):
+        sub_lod = []
+        max_batch_id = sub_lvl[-1]
+        for i in range(max_batch_id.astype(np.int32) + 1):
+            sub_lod.append(np.where(sub_lvl == i)[0].size)
+        return sub_lod
+
+    def add_multilevel_roi(self, rois, target_lvls, lvl_min, lvl_max):
+        rois_idx_order = np.empty((0, ))
+        rois_fpn = []
+        for lvl in range(lvl_min, lvl_max + 1):
+            idx_lvl = np.where(target_lvls == lvl)[0]
+            if len(idx_lvl) == 0:
+                rois_fpn.append((np.empty(shape=(0, 4)), [[0, 0]]))
+                continue
+            sub_lod = self.get_sub_lod(rois[idx_lvl, 0])
+            rois_fpn.append((rois[idx_lvl, 1:], [sub_lod]))
+            rois_idx_order = np.concatenate((rois_idx_order, idx_lvl))
+        rois_idx_restore = np.argsort(rois_idx_order).astype(
+            np.int32, copy=False)
+        return rois_fpn, rois_idx_restore
+
+    def calc_rois_distribute(self):
+        lvl_min = self.roi_min_level
+        lvl_max = self.roi_max_level
+        target_lvls = self.map_rois_to_fpn_levels(self.rois[:, 1:5], lvl_min,
+                                                  lvl_max)
+        rois_fpn, rois_idx_restore = self.add_multilevel_roi(
+            self.rois, target_lvls, lvl_min, lvl_max)
+        return rois_fpn, rois_idx_restore
+
+    def make_rois(self):
+        self.rois_lod = [[100, 200]]
+        rois = []
+        lod = self.rois_lod[0]
+        bno = 0
+        for roi_num in lod:
+            for i in range(roi_num):
+                xywh = np.random.rand(4)
+                xy1 = xywh[0:2] * 20
+                wh = xywh[2:4] * (self.images_shape - xy1)
+                xy2 = xy1 + wh
+                roi = [bno, xy1[0], xy1[1], xy2[0], xy2[1]]
+                rois.append(roi)
+            bno += 1
+        self.rois = np.array(rois).astype("float32")
+
+    def setUp(self):
+        self.op_type = "distribute_fpn_proposals"
+        self.set_data()
+
+    def test_check_output(self):
+        self.check_output()